We continued biochemical studies of mammalian DNA replication proteins. A cDNA for beta-polymerase has been subcloned in expression vectors; the protein has been overproduced in E. coli, purified in mg quantities and sequenced. Structure-function aspects and in vitro DNA repair activities of the recombinant enzyme are being studied. Genomic DNA spanning the gene for human B-polymerase was further characterized. The promoter region was studied by detailed deletion and site mutagenesis using a transient expression system. In other work, we purified a transcription factor for the beta-polymerase gene. In vitro transcription studies of the gene are under way, as well as physical biochemical studies of the sequence-specific binding between the promoter and the purified factor.